This invention relates to a method for the production of presensitized, lithographic printing plates and to novel lithographic printing plates obtained thereby. More particularly, this invention relates to a negative-working, water-developable, bilayer lithographic printing plate comprising a substrate having a hydrophilic surface, said surface being first coated with a layer of a water-soluble, lithographically suitable, photosensitive, negative-working, aromatic diazo composition and top coated with a layer of a water-permeable, water-insoluble, oleophilic, O-epoxyalkylated tetrakis (hydroxyphenyl) ethane resin and ester derivates thereof. Upon imagewise exposure, the exposed areas become water-insoluble and development is effected by washing away the unexposed areas with tap water.
The art in the lithographic printing plate area has always had a problem with development of the image. That is, various chemical developing substances are employed which must be discarded usually through community waste removal facilities. Not only are such developers costly to purchase but they also cause pollution problems on being discarded. Thus, a lithographic printing plate which is developable by ordinary tap water is commercially desirable.